The invention relates to a composite material with a first outer covering layer and a second outer covering layer spaced from the first outer covering layer at a spacing distance, and an intermediate layer between the covering layers.
In the production of composite materials, covering layers, which may consist of metal, plastic, wood veneers, or other laminates, are generally used and any desired intermediate space is produced between them by introducing an intermediate layer of plastic or foamed plastic. The covering layers in sheet form must thereby be fixed at a desired distance from each other and an escape of the plastic, tacky polymer composition must be avoided by a lateral limitation. When using a foamable composition for the intermediate layer, pressure relief must take place in order that the foam can expand freely and is not compressed under the load of a weight. The properties of such composite materials are determined both by the covering layers and by the intermediate layer introduced. Depending on the material structure, the composite effect must be enhanced by additional adhesion promoters or a physically or chemically setting adhesive. A disadvantage here is that solvents or the like are released during these operations and lead to environmental pollution. In the case of relatively small sheet segments or three-dimensionally shaped sandwich components, they must be produced in complex molds which retain the desired contour and close off with a sealing effect the space between the covering layers or sheet elements, in order that the composition forming the intermediate layer, possibly a foamable composition, does not escape from the intermediate space. The material of the intermediate layer located between the covering layers usually has a uniform consistency, so that harder or more compliant regions within a component cannot be produced, or can only be produced in a multi-stage process.
The object of the invention is to provide a composite material which overcomes the above-noted deficiencies and disadvantages of the prior art devices and methods of this kind, and which can be produced without complicated fixing of the distance between the covering layers and which can be brought into a desired three-dimensional contour in a relatively uncomplicated way.
With the above and other objects in view there is provided, in accordance with the invention, a composite material, comprising:
a first outer covering layer;
a second outer covering layer disposed at a spacing distance from the first outer covering layer; and
an intermediate layer arranged between the first and second outer covering layers and formed by at least one natural fiber mat of renewable raw materials and interspersed with material components selected from the group consisting of fusible particles, foamable particles, and curable substances.
In other words, the objects are satisfied with a composite material with a first and a second outer covering layer, in particular of metal, plastics or wood veneer, arranged a distance apart, and an intermediate layer arranged between the covering layers which is distinguished by the fact that the intermediate layer is formed by a t least one natural fiber mat of renewable raw materials which is interspersed with fusible and/or foam able particles and/or curable substances.
The outer covering layers are preferably formed of metal, plastic, or wood veneer.
In accordance with an added feature of the invention, the at least one natural fiber mat is flax, hemp, jute, kenaf, sisal, or a combination of the materials.
In accordance with an additional feature of the invention, the natural fibers of the natural fiber mat have a defined critical temperature, and the fusible particles have a melting point below the critical temperature. Preferably, the melting point lies below 240xc2x0 C.
In accordance with another feature of the invention, the fusible particles are selected from polypropylene, LD or HD polyethylene, EVA, nylon 11, and nylon 12.
In accordance with a further feature of the invention, the natural fiber mat has a natural fiber content of between 30% and 95% and a particle content between 5% and 20%.
Preferably, at least some of the fusible particles are fibrous particles.
In accordance with again an added feature of the invention, the at least one natural fiber mat is one of a plurality of natural fiber mats. The plurality of natural fiber mats have a substantially identical material composition and a substantially identical degree of compaction. In the alternative, they have mutually different material compositions and/or the fiber mats have mutually different degrees of compaction.
In accordance with again an additional feature of the invention, the intermediate layer has a predefined degree of compaction. In a preferred embodiment, the intermediate layer is compacted locally to varying degrees.
In accordance with again another feature of the invention, the spacing distance between the first and second covering layers is approximately inversely proportional to a degree of compaction of the intermediate layer.
In accordance with a preferred variation, the intermediate layer comprises one or more relatively highly compacted natural fiber mat and one or more less highly compacted natural fiber mats.
In a further development, the first and second covering layers are formed of metal (e.g., aluminum, copper, and nickel), thermosetting material, thermoplastic material, wood, laminate, compacted natural fiber layers, or combinations thereof.
In an advantageous development, the composite material is produced endlessly. In the alternative, the first and second covering layers and the intermediate layer are cut-to-size pieces.
In a particularly advantageous development of the invention, the intermediate layer and/or the first and/or second covering layers have punched clearances formed therein.
Preferably, the intermediate layer is provided with reinforcing linings, such as linings with or from glass fibers, carbon fibers, aramid fibers, natural fibers, and reinforcing woven fabric.
In an alternative embodiment, at least one of the first and second covering layers is provided with a decorative material. Preferable decorative materials are polymer films, textile materials, and leather.
In accordance with a concomitant feature of the invention, the intermediate layer is formed of foam, rubber, and/or thermoplastic elastomer.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a composite material, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.